Our client is a group of potentially responsible parties (PRPs) implementing a Remedial Investigation Unilateral Administrative Order to investigate and address environmental impacts associated with historical operations at a crude oil processing facility located in northern Montana.
The Montana Department of Environmental Quality (MDEQ) oversees activities at the Facility in accordance with the Montana Comprehensive Environmental Cleanup and Responsibility Act (CECRA) program. Since 2011, EHS Support has been both the Project Coordinator and Primary Consultant for the Group.
The Facility includes an active crude oil transportation and temporary storage terminal, which has been in operation since the early 1930s. Petroleum hydrocarbon (including light non-aqueous phase liquid [LNAPL]) impacts to soil, groundwater, surface water, colluvium, and sediment have been reported. The State of Montana began investigations in 1988. In 1994, MDEQ formally listed the Facility as a high priority state Superfund site.
The technical scope for this project includes completion of a supplemental remedial investigation (RI), supporting the finalization of a human health and ecological risk assessment (RA), development of a feasibility study (FS), and implementation of remedial actions. As part of the FS, major studies have been completed on natural source-zone depletion (NSZD), LNAPL mobility and recoverability, and the feasibility of hydraulic containment and enhanced (bio-stimulation) bioremediation of LNAPL soil and groundwater impacts.
The primary objectives of the RI were to address data gaps in the understanding of the conceptual site model (CSM) of the distribution, fate, and transport of impacted site media. The next milestone will be completion of the FS.
The technical team continues to evolve its approach to routine groundwater monitoring activities through assessing the extent of NSZD and monitoring of groundwater parameters indicative of natural attenuation.
EHS Support completed an aggressive schedule of field work and reporting with the constraints of a limited field season in northern Montana, all while transitioning across several MDEQ project managers. Findings from the supplemental RI have shown the following, which will help limit the magnitude and duration of remediation required to be performed at the Facility:
- Robust natural attenuation of petroleum hydrocarbon impacts in groundwater beneath the Facility
- Decrease in petroleum hydrocarbon impacts to surface water and colluvium to below applicable criteria, likely eliminating the need for remediation of these media as previously expected
- Limited petroleum hydrocarbon impacts to soil and corresponding low risk to human health from soil impacts.